The present invention relates generally to apparatus and a method for determining the skin type of an individual, and more particularly, to electronic apparatus utilizing a light source which is transmitted through an oil sample taken from the skin of an individual.
As is well known in the cosmetics, dermatology and pharmaceutical fields, a film or deposit of natural oil is present on the skin surface of a person. The formation of this oil film and its deposition on the skin is governed by the sebaceous glands which become active at about the time of puberty and continue to increase in activity until the person reaches the early twenties. Thereafter, the sebaceous glands then slowly diminish in efficiency and thus, the degree of oiliness of the skin is lessened as the person ages. It is also generally known that aged skin is a drier skin, e.g., there is less oil content.
Skin type may be divided into three broad categories with respect to skin oil content: (1) normal; (2) oilier than normal; and (3) drier than normal. Specific skin care and make-up products are designed to conform and to perform their functions according to skin type.
To determine an individual's skin type, a dermatologist will generally visually observe the patient's skin and relate the condition to the patient's age. Dermatologists also examine the skin surface for shininess as well as ease of transference of skin oil to a glass slide or test paper. The presence or absence of selected pathologic findings, such as blackheads, redness, scaling and the location of same, also contribute to a reasonably accurate determination of skin type.
To date, however, no reliable instrumentation has been available which will provide a truly objective evaluation and determination of the skin type of an individual, either by physicians or lay persons, e.g., cosmetologists.
Conventional apparatus for measuring the amount of oil or sebum secreted by the skin of a living subject generally fall into two classes. One such class of device is described in U.S. Pat. No. 4,224,950, to Bore et al, wherein the change in transparency of a glass plate due to oil adhering thereto is measured. The other class of devices are those which typically use chemical analysis methods, such as diffusion, gas chromatography and, as disclosed by Tur et al, U.S. Pat. No. 3,906,933, electrostatically charged printing surfaces which obtain an imprint of the skin. However, the drawback of this second class of devices is that although they may be intended for use by unskilled personnel, an analytical evaluation must later be conducted by skilled personnel, which evaluation is both costly and time consuming.
The device described in U.S. Pat. No. 4,244,950 to Bore et al is a sebumeter which is intended to evaluate the activity of the sebaceous glands by means of a sample of the sebum secreted by the skin in the vicinity of the forehead. This device comprises a casing for holding a removable sample-holder which projects from the casing. A translucent element carried by the sample-holder can be applied to the forehead of the subject. A scale is located within the casing and carries at least one reference mark which, upon illumination of the translucent element by means of a self-contained light source, enables the user of the device to read, by observation of the reference mark, the amount of sebum deposited on the sample-holder.
While such a device may be useful for determining the amount of sebum on the skin surface of one individual, some difficulty and a great deal of inconvenience arises when the glass plate used therewith must be changed. In addition, the device disclosed therein is mechanical in nature and is subject to mechanical failure, particularly the calibrated compression spring which is secured to the sample-holder. Another drawback of the Bore et al device is that it requires a certain period of time during which the user of the device must observe the location of the reference mark in order to determine the amount of sebum present on an individual's skin. Finally, due to the size of the Bore et al device, it is subject to easily being damaged when used at cosmetic counters, either by being dropped onto the counter, or onto the floor around the counter, where it may be subjected to crushing by salespersons or customers.
When a device for determining skin type is to be utilized by untrained or unskilled personnel, such as cosmetic counter salespersons, it is necessary that means be provided within the device such that accurate readings can be easily obtained. This is especially true with electronic devices which may be sensitive to ambient light and/or temperature, line voltage variations, battery life, rough handling, variations in probe construction, etc. The present invention is therefore provided with a calibration circuit to insure that accurate readings are continuously obtained with the subject skin type determining device. The method of calibrating the disclosed device is simple, rapid and accurate and thus is ideally suited for use by untrained or unskilled users.
Another conventional but non-relevant device is shown in U.S. Pat. No. 3,241,431 to Brutten et al, and discloses method and apparatus for the measurement of fingerprint density by measuring the opacity of a strip of translucent material carrying a fingerprint. The method of calibrating this device is complex and time consuming and therefore susceptible to error.
In designing a useful skin type determining device, it is important to consider the environment in which the device will be used. Typically, cosmetic counters are located in department and specialty stores. The selling areas in these stores are generally open and are illuminated by fluorescent lighting. Thus, in order to successfully design a reliable skin type determining device which utilizes optical principles, care must be taken to minimize the effects of outside and ambient light on the optical measurements performed by the device. Thus, the present invention utilizes an infrared light source of approximately 920 nm. In addition, the detected light passing through the probe is integrated prior to calculating skin type, thus compensating for the known fact that oil on the skin surface of a person may not be homogenous over a small area of skin.
In a known light absorptivity device, U.S. Pat. No. 4,281,932, to Young, an LED light source is utilized in combination with a light sensing device to determine the quantity of light passing through a translucent medium. The reading is stored and then a second reading is made with a reference medium. The device indicates when the measured absorptivity is equal to the known absorptivity, and thereby the absorptivity of the measured medium is known. The only relevance of this device to the present invention is its use of an LED light source. Young does not disclose a specific reason for using an LED as a light source, and, in fact, also discloses the use of an incandescent light source. Furthermore, the device of Young is disclosed at col. 2, line 11 to embody a light-tight housing 10 in which either light source is mounted.
In the cosmetic field, it is desirable that customers receive prompt and accurate answers so that the greatest number of customers can be evaluated within any given time period thereby maximizing the sales of cosmetics to these customers. The instant device readily fulfills this need.